Aralkylated dihydroquinolines



Patented Jan. 20, 1953 ARALKYLATED .DIHYDROQUINOLINES JosephR. Ingram, .Nitro, wflva ass'ignor to -Mon- .santo .Chemical Company, ;S.t. .Louis, iMo., acorporation of Delaware No Drawing. .Original appliea'tionNoveniber 251,

1948, Serial .No. 61,911. Divided and this application July '2, 1949, Serial 'No. 102,960

also.

.4 Claims. 01. 26018.8..3)

line bodies are a new 'family of chemical .com-

pounds 'and are representative of a highly effective and economical .class of rubber antioxidants. The new chemicals are obtained by "reacting a 1,2-dihydroquinoline with a suitable aralkylating agent and are to be distinguished from alkyl, aryl, and other substituted dihydroquinolines known to possess antioxidant properties. Thus substituted dihydroquinoline antioxidants have been obtained by reacting a substituted aniline with a ketone but these products do not possess the properties of the new class. The new chemicals are not only adaptable to rubber vulcanizates containing carbon black for improving flexing properties but are suitable for white rubber stocks In contrast to most rubber antioxidants containing nitrogen, they are resistant to staining and discoloration.

Aralkyl substituted 1,'2-dihydroquinolines may be prepared conveniently bya number of methods, for example, by condensing an aralkyl halide with a 1,2-dihydroquinoline in the presence of a catalyst such as aluminum chloride or zinc chloride. Suitable halides are benzyl chloride, diphenyl methyl chloride, triphenyl methyl chloride, phenethyl chloride, chlor propyl benzene, indanyl chloride, and the like. Anothermethodofpreparation is to react an aromatic substituted olefinic hydrocarbon with a 1,2-dihydroquinoline in the presence of a non-oxidizing catalyst. Among the aromatic substituted olefinic hydrocarbons which will readily react are styrene, o-, -,m-, and ;pmethyl styrene, o-, m-, and p-ethyl styrene, the diethyl styrenes, allyl benzene, the divinyl benzenes, the phenyl butadienes, a and 5 vinyl naphthalene, vinyl pyridine, indene, a methyl indene,

and their hydroxy and alkoxy substituted analogues. Mixtures of the above materials are also contemplated.

The chemical structure of the products obtained by reacting a 1,2-dihydroquinoline with an aralkyl halide or an aromatic substituted olefinic hydrocarbon is not known but the reaction is believed to involve, principally, the carbon atom and caustic, and taken up with toluene.

containing .the halogen .substituent .o-f the-analkyl halide or :the unsaturated carbon atom nearest thearomatic nucleus of :the aromatic substituted olefinic hydrocarbon and a carbon :atom in the nucleus of the dihydroduinoline. However, the present invention is not limited to any assumption as-to chemical structure 'but pertains broadly to the products obtained :by reacting an aralkyll halide or an aromatic substituted olefinic hydrocarbonwith a 1,2-dihydroquinoli-ne.

As examplary of the preparation of the new chemicals the following examples are illustrative --and are not to "be construed as limitative thereof.

EXAMPLE ,1

To a 3-neck flask equipped with-a thermometer, a stirrer, and a reflux condenser, containing 34.6 parts by weight (substantially 02 met) of 2,2,4- trimethyl 1,2-dihydroquinoline was added 127.6 parts by weight (substantially 02 mol) of indene and 75 ml. of benzene. While agitating, 26.6 parts by weight .-.(substantially 0.2 mol) of anhydrous aluminum chloride was added. The mixture was then heated at the reflux-temperature forlhours. The mix was'cooled and placed in afdistilling apparatus containing 130 parts-by "weight of a 25% sodium hydroxide "solution and thebenzene distilled off. Thereuponthemix was steam distilled'to remove {the last traces -of--benzene and unreacted indene. The residue was washed free of alkali and dried at 60 C. The dried product believed to be an indanyl substituted 2,2,4-t-rimethyl 1,2-dihydroquinoline was found to have a meltingpoint of approximately C. The yield was about EXAMPLE 2 To a 3-neck'fiask equipped withathermometer, a stirrer, and a reflux condenser containing -137:3 parts by weight (substantially 0.1mol) of 2,2,4- trimethyl l ,2-dihydroquinoline was added 10.4

partsby weight (substantially 0.1'mo1) of styrene.

While agitating, 13.3 parts by weight (substantially 0.1 mol) of aluminum chloride was added. The reaction vessel was then placed in a steam bath and heated for2 hours. A solid resinous material developedwhich was-washed with water Upon removal of the solvent26.5 parts(96% yield) ;by weight of a resinous-product was recovered.

3 EXAMPLE 3 To a suitable reaction vessel containing 26 parts by weight (substantially 0.15 mols) of 2,2,4- trimethyl 1,2-dihydroquinoline and 22.2 parts by weight (substantially 0.15 mol) of anethole (pmethoxy allyl benzene) was added 20 parts by .weight (substantially 0.15 mol) of aluminum chloride. The contents of the reaction vessel were heated for 3 hours at 60 to 80 C. Upon cooling the reaction product was washed with water and caustic. and taken up with benzene. Upon removal of the solvent 39 grams (80% yield) of a resinous like product having a melting point of about 80 C. was obtained.

EXAMPLE 4 taken up with benzene and washed free of residual acid. Upon removal of the solvent approximately 68 parts by weight (about 100% yield) of a resinous product was obtained.

EXAMPLE 5 A suitable reaction vessel containing a reaction mix consisting of 4'7 parts by weight (substantially 0.3 mol) of indanyl chloride and 51.9 parts by weight (substantially 0.3 mol) of 2,2,4-trimethyl 1,2-dihydroquinoline dissolved in carbon disulfidewas heated for 2% hours at approximately 40-46 C. in the presence of 40 parts by Weight (substantially 0.3 mol) of anhydrous aluminum chloride. The carbon disulfide was removed and the reaction product was washed with water and caustic, and taken up with benzene. Upon removal of the solvent 80 parts by weight of a resinous product was isolated. This product was not unlike the residual product of Example, 1.

EXAMPLE 6 (substantially 0.2 mol) of 2,2,4-trimethyl 1,2-

dihydroquinoline dissolved in 30 parts by weight (substantially 0.38 mol) of benzene was admitted to the reaction vessel and the contents heated for 2 hours at the reflux temperature. cooling the reaction product was washed with water and caustic and the residual benzene distilled oiT leaving 74 parts by weight (95% yield) of a reddish yellow resinous product believed to be principally triphenyl methyl substituted 2,2,4- trimethyl 1,2-dihydroquinoline. The resinous product was distilled under diminished pressure and the residue found to have a melting point of about 93 C. 7

While in the above examples only one dihydroquinoline reactant has been described, other 1,2-dihydroquinolines, mixtures of dihydroqui nolines, and the crude reaction product of 1 mol of arr aromatic amine and 2 mols of an aliphatic The Upon

4 ketone, can be aralkylated in a like manner to produce similar products having useful oxidative inhibiting and non-discoloring properties. For example, 2 methyl-2,4-diethyl-1,2-dihydroquinoline, 2-methyl-2,4-diisopropyl-1,2-dihydroquinoline, and the crude reaction product of 1 mol of aniline and 2 mols of acetone are contemplated.

As specific embodiments of the invention portraying the age-resistant properties of aralkyl subst1tuted 1,2-d1hydroqu1nol1nes, rubber stocks were compounded comprising Parts by weight A B O D Smoked sheets rubber 100 100 100 100 b1 c 50 50 50 5 5 5 2 2 2 3 3 3 f 3 3 3 Mercaptobenzothiazole 75 75 Indanyl chloride-2,2,4trimethyl 1,2'dihydroquinoline reaction product 1.0 Styrene-2,2,4-trimethyl 1,2-dihydroquinoline reaction product 1.0 Anethole-2,2,4-trimethyl 1,2-dihytdroqumoline reaction prod- 1 0 no The rubber stocks so compounded were vulcanized in a press for 60 and 90 minutes respectively at 135 C. Test strips were out from the vulcanized stocks and artificially aged for 6 and 9 hours respectively at 121 C. in an air bomb under pounds per square inch pressure. The results are as follows:

Table I Tensile in Modulus 1n Ultip. s. i. after p. s. i. Ult. mate aging in air elong., tensile bomb at 121 C. percent in p. s. i. 300% 500% 6 hrs. 9 hrs.

60 min. cure at Stock A. 1, 820 3, 803 690 4, 650 3, 047 l, 670 Stock B 1, 793 813 593 4, 620 3, 167 l, 853 Stock C l, 863 3, 827 590 4, 673 3, 097 1, 970 Stock D. l, 827 3, 973 517 4, 150 l, 710 783 min. cure at Stock A. 1, 923 4, 070 533 4, 360 2, 977 1, 427 Stock B 2, 4, 047 573 4, 550 3, 025 l, 203 Stock 0. 2,093 4, 177 527 4, 460 3,157 1,430 Stock D 2, 050 4, 227 510 313 1,695 955 Table II Kilocycles to failure Stock A B C D Unaged 168 203 167 138 Aged 9 hours at 121 C. in air bomb 184 128 161 25 Aged 120 hours at 70 C. in

oxygen bomb 55 78 91 l As exemplary of the non-discoloring properties of the new antioxidants, the following stock was compounded:

Pale crepe rubber 100 Zinc oxide 60 Lithopone Sulfur 2 Benzothiazyl thio benzoate .675 Diphenylguanidine-phtha1i acid reaction product .825 Parafiin .25 Styrene 2,2,4 trimethyl 1,2 dihydroquinoline reaction product 1.0

and vulcanized in a press for 45 and 60 minutes respectively at 126 C. After 9 hour air bomb aging at 121 C. and 80 pounds per squar inch pressure, the tensile strengths for the 45 and 60 minute cures, respectively, were 2840 and 2820 pounds per square inch. Test strips cut from the 45 and 60 minute cured rubber stock showed only a slight yellowing efiect after exposure to the rays of a sunlamp for ten days. Other aralkylated 1,2-dihydroquinolines such as the anethole- 2,2,4 trimethyl 1,2 dihydroquinoline reaction product, the triphenyl methyl chloride-2,2,4- trimethyl-1,2-dihydroquinoline reaction product and the benzyl chloride-2,2,4-trimethyl-1,2-dihydroquinoline reaction product similarly exhibited remarkable resistance to light deterioration upon exposure to sunlamp rays.

Obviously the examples set forth above show that rubber compositions containing an aralkylated 1,2-dihydroquinoline are markedly resistant to the deteriorating influences of flexing, heat, oxidation, and light, and while the above data describes only specific compounds of the new class of rubber antioxidants, all members of said class are advantageous in carrying out the objects of the invention.

For most purposes 1 percent of the new family of rubber antioxidants based upon the weight of the rubber afiords good protection with an ample margin of safety but amounts as small as 0.2 percent are effective. Amounts above 1 percent, as for example 2.5 percent or more, may be employed where desired although usually without added benefit.

The new chemicals may be employed as antioxidants in other rubbers than natural rubber, such as rubber substitutes, synthetic rubber, and the like whether or not admixed with fillers, pigments, accelerators, etc.

The new antioxidants may be incorporated into a rubber or rubber like substance by milling or mastication, added to rubber latices, or any equivalent procedure such as applying them to the surface of a vulcanized or unvulcanized rubber in the form of a powder or paste.

While certain specific embodiments of this invention have been described in detail herein, it is to be understood that the invention is not limited for many modifications may be resorted to such as varying the proportions of the new antioxidants and incorporating in the stock other vulcanization accelerators than the above disclosed, without departing from the spirit or scope oi the invention.

This invention is a division of co-pending application Serial No. 61,911 filed November 24, 1948.

What is claimed is:

1. The method of making a resinous aralkyated dihydroquinoline antioxidant which comprises heating in the presence of one mole of a Friedel- Crafts catalyst one mole of a 1,2-dihydroquinoline containing only carbon, hydrogen and one nitrogen atom and substantially one mole of a reagent selected from the group consisting of aralkyl chlorides, indanyl chloride and aromatic substituted olefins containing 8 to 12 carbon atoms and not more than two CH2:CH- groups as the sole olefinic constituents.

2. The method of making a resinous aralkylated dihydroquinoline antioxidant composition which comprises heating in the presence of one mole of a Friedel-Crafts catalyst one mole of 2,2,4-trimethyl-1,2-dihydroquinoline and substantially one mole of styrene.

3. The method of making a resinous aralkylated dihydroquinoline antioxidant composition which comprises heating in the presence of one mole of a Friedel-Crafts catalyst one mole of 2,2,4-trimethyl-1,2-dihydroquinoline and substantially one mole of indene.

4. The method of making a resinous aralkylated dihydroquinoline antioxidant composition which comprises heating in the presence of one mole of a Friedel-Crafts catalyst one mole of 2,2,4-trimethyl-1,2-dihydroquinoline and substantially one mole of benzyl chloride.

JOSEPH R. INGRAM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,160,200 Dunbrook et al May 30, 1939 2,203,899 Dunbrook et al. June 11, 1940 2,268,419 Paul Dec. 30, 1941 2,400,500 Gibbs May 21, 1946 2,530,774 Kehe Nov. 21, 1950 

1. THE METHOD OF MAKING A RESINUOUS ARALKYATED DIHYDROQUINOLINE ANTIOXIDANT WHICH COMPRISES HEATING IN THE PRESENCE OF ONE MOLE OF A FRIEDELCRAFTS CATALYST ONE MOLE OF A 1,2-DIHYDROQUINOLINE CONTAINING ONLY CARBON, HYDROGEN AND ONE NITROGEN ATOM AND SUBSTANTIALLY ONE MOLE OF A REAGENT SELECTED FROM THE GROUP CONSISTING OF ARALKYL CHLORIDES, INDANYL CHLORIDE AND AROMATIC SUBSTITUTED OLEFINS CONTAINING 8 TO 12CARBON ATOMS AND NOT MORE THAN TWO CH2=CH- GROUPS AS THE SOLE OLEFINIC CONSTITUENTS. 